1. Technical Field
This disclosure generally relates to computer systems, and more specifically relates to sharing a single IP address among multiple virtual machines residing on one or more physical host computers.
2. Background Art
A single host computer may hold multiple virtual instances of a computer referred to as a virtual machine. A virtual machine is sometimes defined as an efficient and isolated duplicate of a real machine. A virtual machine is thus a duplicate or instance of a virtual computer residing on a physical host computer. A virtual machine is sometimes also called a logical partition. A principle advantage of a virtual machine system is that multiple operating system (OS) environments can co-exist on the same computer in isolation from each other. In addition, a virtual machine can provide an instruction set architecture that is different from that of the real machine. A virtual machine can be utilized to improve application provisioning, maintenance, high availability and disaster recovery.
Virtual machines residing on a physical host computer typically must share a physical network interface of the host computer. The physical network interface of the host computer is connected to an external network. As used herein, an external network is any network residing outside of a single physical machine and may/may not be indirectly contacted through a series of firewalls. In some cases, it is advantageous to have a single IP address from the external network address space assigned to the physical interface of the host computer. Virtual machines residing on the host have their own virtual network interfaces connected to the same external network via the host physical interface. In the prior art, there have been various approaches to having multiple virtual machines use the same physical network interface.